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Utilities can use off-peak electricity to compress air and store it in airtight underground caverns. When the air is released from storage, it expands through a combustion turbine to create electricity.
How It Works
Off-peak electricity is used to power a motor/generator that drives compressors to force air into an underground storage reservoir. This process typically occurs when utility system demands and electricity costs are the lowest. When electric power demand peaks during the day, the process is reversed. The compressed air is returned to the surface, heated by natural gas in combustors and run through high-pressure and low-pressure expanders to power the motor/generator to produce electricity.
Advantages
Nearly two-thirds of the natural gas in a conventional power plant is consumed by a typical natural gas turbine because the gas is used to drive the machine's compressor. In contrast, a compressed-air storage plant uses low-cost heated compressed air to power the turbines and create off-peak electricity, conserving some natural gas.
Applications
The concept of compressed-air energy storage to help generate electricity is more than 30 years old. Two plants currently exist — an 11-year-old plant in McIntosh, Alabama, and a 23-year-old plant in Germany, both in caverns created by salt deposits.
For more information on compressed air energy storage, see the comprehensive list of links provided by DOE's Energy Efficiency and Renewable Energy Network.
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